potential of some fungal and bacterial species in bioremediation of heavy metals

213

Journal of Nuclear Physics, Material

Sciences, Radiation and Applications

Vol. 1, No. 2 February 2014

pp. 213–223

©2014 by Chitkara University. All Rights

Reserved.

DOI: 10.15415/jnp.2014.12018

Potential of Some Fungal and Bacterial Species in Bioremediation of Heavy Metals

Raman Kumar1, Prem singh2, Bhupinder Dhir3,*, Anil K Sharma1 and Devinder Mehta4

1Department of Biotechnology, M.M. University, Mullana-133203, Haryana, India2Department of Physics, S.D. College, Ambala Cantt.-133001, Haryana, India3Department of Genetics, South Campus, Delhi University, New Delhi-110021, India4Department of Physics, Panjab University, Chandigarh-160014, India

*E-mail: [email protected]

Abstract Microorganisms including fungi and bacteria have been reported to extract heavy metals from wastewater through bioaccumulation and biosorption. An attempt was, therefore, made to isolate bacteria and fungi from sites contaminated with heavy metals for higher tolerance and removal from wastewater. Bacterial and fungal isolates were obtained from the samples collected from Karnal, Ambala and Yamunanagar districts of Haryana using enrichment culture technique. Bacterial and fungal isolates with tolerant up to 100 ppm concentration of heavy metals (Pb, Cd, Cr) were tested for their removal from liquid media containing 50 ppm concentration of Pb, Cd and Cr each. Five fungi (Penicillium chrysogenum, Aspegillus nidulans, Aspergillus flavus, Rhizopus arrhizus, Trichoderma viride) were also included in this study. Fungi Aspergillus nidulans, Rhizopus arrhizus and Trichoderma viride showed maximum uptake capacity of 25.67 mg/g for Pb, 13.15 mg/g for Cd and 2.55 mg/g of Cr, respectively. The maximum uptake capacity of tolerant bacterial isolates - BPb12 and BPb16, BCd5 and BCr14 were observed to be ~ 45 mg/g for Pb, 2.12 mg/g for Cd and 3.29 mg/g for Cr, respectively. This indicated the potential of these identified fungi and bacteria as biosorbent for removal of high concentration metals from wastewater and industrial effluents.

Keywords: Heavy metals; Biosorption; Wastewater; Fungi; Bacteria

1. IntRoDuctIon

Increased use of metals and chemicals in process industries has resulted in generation of large quantities of effluent that contain high level of toxic heavy metals. Their presence due to lack of proper disposal poses environmental problems due to their non-degradable and persistence nature. These metals enter into human beings and animals through food chain and cause many metabolic disorders [1,2]. Unlike organic chemicals, metals persist in environment indefinitely posing threats to all the organisms which are exposed to them. Wastewater may be of simple composition if derived from single industry, e.g., electroplating wastewater, or in other cases could be a heterogeneous mix (coming from different industries) of many dissolved metal ions at various pH with salts, colloidal and particulate matters present as well. Using microorganisms as biosorbents for heavy metals is an attractive alternative to existing methods such as chemical precipitation, chemical oxidation or reduction, electrochemical treatment,

Kumar, R.Singh, P.

Dhir, B.Sharma, A.K.Mehta, D.

214

filtration, ion exchange and membrane technologies for toxicity reduction and recovery of valuable metals from industrial effluents, because of good performance and low cost of biosorbent material [3]. These processes may be ineffective or expensive, especially when dissolved heavy metals concentration in the solution ranged from 1-100 mg/l [4]. Bioremediation of heavy metals involving microorganisms could be brought about by employing methods such as bio-accumulation, biosorption, bio-precipitation and uptake by purified biopolymers from microbial cells [5,6]. Therefore, it is desirable to remove heavy metals from wastewater through environment friendly low cost technology before its use in agriculture or discharge into water bodies [7-10].

Heavy metal resistant microbes might be present in heavy metal contaminated sites. The resistance and efficiency of microbes for removal of heavy metals vary greatly. Therefore, there is need to isolate and screen heavy metal tolerant fungi and bacteria from heavy metals contaminated sites. The present study is an attempt to isolate and screen heavy metal tolerant (Pb, Cd, Cr) fungi and bacteria. Their efficiency to remove heavy metals from liquid media was also evaluated under laboratory conditions.

2. MAteRIAl AnD MetHoDS

2.1 collection of samples

Samples of sewage, sludge and industrial effluents were collected in sterilized containers from sewage treatment plants at Karnal, Ambala and Yamunanagar districts of Haryana. These samples were brought to laboratory and kept in refrigerator at 4°C for further processing.

2.2 Preparation of heavy metal solution

The 1000 ppm stock solutions of Pb, Cd and Cr were made in double distilled water using Pb (NO

3)

2, CdCl

2, and K

2Cr

2O

7 (SD Fine-Chem Ltd., Mumbai, India). The 25,

50, 100 and 400 ppm solution of these heavy metals was prepared from 1000 ppm stock solution by dilution with double distilled water. The stock solution of heavy metals was sterilized separately through bacteriological filters and added to sterilized potato dextrose and nutrient broth to make its concentration 25, 50 and 100 ppm.

2.3 Isolation and screening of fungal and bacterial isolates for tolerance to heavy metals

Fungal isolates were isolated from samples of sewage, sludge and industrial effluents by serial dilution method using potato dextrose agar (Hi-Media, Mumbai, India) containing 25 ppm of Pb, Cd and Cr individually. A serial dilution of each sample was made up to 106 and one ml of dilution 104 and 106 was added in sterilized petri plates in duplicate. 20 ml PDA medium containing 25 ppm of one of these heavy metals was poured in the petri plates and incubated at 28°C for 96 h. The colonies

Potential of Some Fungal and Bacterial Species

in Bioremediation of Heavy Metals

215

of predominant genera of fungi were picked up and purified by streak plate method. Heavy metal tolerant (25 ppm) fungal isolates were further screened for tolerance to Pb, Cd and Cr at 50 and 100 ppm of heavy metals individually on PDA. All the fungal isolates were streaked on PDA medium containing 50 and 100 ppm of each of the three heavy metals separately. Streaking of fungal isolates on normal PDA medium served as control (normal growth) for comparison of growth of fungal isolates on PDA medium containing different concentration of heavy metals. Observations on growth of fungal isolates were made after 96 h of incubation. The growth of fungal isolates was recorded as normal growth or absent growth in comparison to control. Five fungi (Penicillium chrysogenum, Aspegillus nidulans, Aspergillus flavus, Rhizopus arrhizus, Trichoderma viride) were also included in this study. Similarly, for isolation of bacterial isolates, a serial dilution of each sample was made up to 107 and one ml of dilution 105 and 107 was added in sterilized petri plates in duplicate. 20 ml nutrient agar (NA) medium containing 25 ppm of one of these heavy metals was poured in these petri plates and incubated at 37°C for 48 h. The colonies of predominant genera of bacteria were picked up and purified by streak plate method. Heavy metal tolerant (25 ppm) bacterial isolates were further screened for tolerance to Pb, Cd and Cr at 50 and 100 ppm of heavy metals individually on NA and were processed in the same way as mentioned above.

2.4 uptake of heavy metals by fungal and bacterial isolates from liquid media

The highly heavy metal tolerant fungal isolates were evaluated for uptake of heavy metals in potato dextrose broth medium containing 50 ppm concentration of different heavy metals Pb, Cd and Cr individually in triplicate. Potato dextrose broth containing 50 ppm of one of the heavy metals was dispensed in100 ml lots to 250 ml conical flasks and sterilized at 15 lbs/psi for 15 min. These flasks were inoculated with 1 ml of freshly prepared spore suspension (106 to107 spores/ml) of each fungal isolate and put on shaker at 150 rpm at 28°C for 96 h. Un-inoculated flasks containing PD broth of 50 ppm concentration of different heavy metals served as control. Fungal growth was harvested after 96 h through filtration using Whatman filter No. 42. The harvested fungal biomass was rinsed with double distilled water 3-4 times and dried in hot air oven at 80°C for 18 h. The dried fungal biomass was weighed and heavy metal concentration in it was estimated by digestion with nitric acid and perchloric acid (ratio = 3:1). The digested fungal biomass was filtered through Whatman filter No. 42 and made the volume of filtrate to 50 ml in volumetric flask.

Similarly, in case of highly efficient bacterial isolates, 1 ml of freshly prepared cell suspension (108 to109 cells/ml) of each bacterial isolate inoculated in to sterilized Nutrient broth containing 50 ppm of one of the heavy metals (Pb, Cd, Cr) and put on shaker at 150 rpm at 37°C for 48 h. Un-inoculated flasks containing Nutrient broth of 50 ppm concentration of different heavy metals served as control. The bacterial growth was harvested by centrifugation at 5000 rpm for 10 minutes after 48 h and washed with phosphate buffer saline (PBS). The harvested bacterial biomass was dried in hot air oven

Kumar, R.Singh, P.


216

at 80°C for 18 h and digested in the same way as mentioned above. The heavy metals concentration in digested fungal and bacterial biomass was estimated [11] by Atomic Absorption Spectrophotometer (GBC932, Semi-automatic). All the experiments were conducted in triplicate and average values are expressed for analysis.

The uptake of heavy metal by fungal and bacterial biomass was calculated using the equation:

q mg/g

1000CV

We ( )=

(1)

where qe is concentration of heavy metal accumulated by fungal/bacterial biomass

in (mg/g), C is concentration of heavy metal (ppm); V (ml) is the volume of the aqueous medium, and W is the dry weight (g) of the fungal/bacterial biomass.

3. ReSultS AnD DIScuSSIonS

3.1 Isolation and screening of heavy metal tolerant fungi and bacteria

Fungal enzymes degrade the heavy metals by incorporating them in their metabolic pathways and by utilizing them as their carbon and energy source. Fifty six fungal isolates tolerant to heavy metals were isolated from samples of sewage, sludge and industrial effluent contaminated with heavy metals such as Pb, Cd and Cr using standard methods [12]. This included 24 isolates tolerant to Pb, 8 isolates tolerant to each of Cd and Cr, 19 fungal isolates and 5 fungi (Penicillium chrysogenum, Aspegillus nidulans, Aspergillus flavus, Rhizopus arrhizus, Trichoderma viride) tolerant to Pb were further screened for their tolerance to Pb at 50 and 100 ppm of Pb. Data indicated decrease in number of isolates tolerant to Pb at higher concentration of Pb. Out of twenty four fungal isolates tolerant to Pb at 25 ppm, only 10 isolates could tolerate Pb at 100 ppm. Similar trend was observed for screening of fungal isolates for their tolerance to Cd and Cr. In case of bacteria, total 43, 14 and 10 bacterial isolates showed tolerance to 25 ppm of Pb, Cd and Cr, respectively. Out of these isolates, only 14, 4 and 4 isolates were tolerant to 100 ppm of Pb, Cd and Cr, respectively. This indicated inhibition of growth of the fungal and bacterial isolates at higher concentration of heavy metals. Similar observations about toxic effect of higher concentration of heavy metals on growth of fungi and bacteria have been reported [1, 13].

3.2 uptake of Pb by fungal and bacterial isolates from liquid media

The maximum uptake of 25.67 mg/g of Pb was observed in Aspergillus nidulans. Minimum uptake of Pb (5.86 mg/g) found in A. sp. (Table 1). The bacterial isolates BPb12 and BPb16 showed the maximum uptake of Pb with nearly equal values ~ 45 mg/g (Table 2). The minimum uptake of 0.69 mg/g was observed for BPb24. Wherever there was less growth, there was higher uptake of Pb and vice versa. The highest uptake of Pb by A. nidulans and bacterial isolate BPb12 and BPb16 indicated more binding sites



217

on cell wall of these microorganisms (fungi, bacteria) and their potential as biosorbent to remove Pb from industrial wastewater containing higher concentration of Pb. A. niger was capable of removing 15.6 and 34.4 mg g−1 copper (II) and lead (II) at 100 mg/l copper (II) and lead (II) concentration, respectively [35]. Polyporous versicolor and Phanerochaete chrysosporium were effective in removing Pb (II) from aqueous solutions with maximum absorptive capacity of 57.5 and 110 mg Pb (II)/g dry biomasses respectively [45]. Removal of lead ions from aqueous solutions by non-living biomass of Penicillium chrysogenum was 116mg/g dry biomass [46]. The percentage removal of lead by Baciilus Vesicularis was decreased when the initial lead concentration increased from 80 to 600 mg/l [36]. The removal of lead from an aqueous solution by biomass of A. niger was observed in this study lower than other studies such as Faryel et al. [37]. However, the observed removal of Pb2+ in this present work was consistent with the findings of Jianlong et al. [38]. The results showed that A. niger is suitable for using as Pb2+ accumulators in waste water. Similar results with respect to differential Pb uptake by different fungi and bacteria were reported by earlier workers [14-21].

3.3 uptake of cd by fungal and bacterial isolates from liquid media

The maximum uptake (13.15 mg/g) of Cd was observed in Rhizopus arrhizus. Minimum uptake of Cd (0.51 mg/g) was observed in Penicillium chrysogenum (Table 3). The maximum uptake (2.12 mg/g) of Cd was observed in BCd5 and minimum (0.34 mg/g) in BCd9 (Table 4). The highest uptake of Cd by R. arrhizus and BCd5 indicated their potential as biosorbent and efficacy to remove Cd from aqueous solution. The basidiomycetes Phanerochaete chrysosporium, Pycnoporus cinnabarinus and Pleurotus ostreatus stopped growing when a concentration of 11.2 mg/l of cadmium was added to their culture medium [39]. P. chrysosporium was used to biosorp cadmium (II), lead (II), copper (II) and the adsorption capacities reached 23.04, 69.77 and 20.33mg/g dry biomass, respectively [47]. Akar and Tunali [48] found that maximum biosorption capacities of Cd (II) and Cu (II) ions on B. cinerea were found to be 17.03 mg/g and 9.23 mg/g, respectively. P. aeruginosa was found to detoxify Cd2+ through production of intracellular cadmium-binding proteins [40]. Similar results with respect to biosorption of Cd and other heavy metals by fungi and bacteria heave been reported earlier [14, 16-18, 22-26].

3.4 uptake of cr by fungal and bacterial isolates from liquid media

The maximum uptake (2.55 mg/g) and minimum uptake of Cr (0.23 mg/g) was observed in (Table 5) T. viride and Aspergillus nidulans in PD broth containing 50 ppm of Cr, respectively. With respect to bacterial isolates, the maximum uptake (3.29 mg/g) of Cr was observed in BCr14 and minimum (0.11 mg/g) in BCr17 (Table 6). The highest uptake of Cr by T. viride and BCr14 indicated their efficiency to remove Cr from aqueous solution containing higher concentration of Cr. At 25 mg/l concentration of Cr (VI), B. sp. and Pseudomonas fluorescens recorded maximum Cr (VI) accumulation [41]. Vasanthy reported that B. sp. was effective in Cr removal up to 83.4 per cent at 10 mg/l

Kumar, R.Singh, P.


218

and 79.1 per cent at 50 mg/l concentration after 72 hours of incubation [42]. Cell free extracts of B. sp. JDM-2-1 and Staphylococcus capitis showed maximum reduction of Cr at concentration of 10 μg Cr (VI)/ml, respectively [43]. Nourbaksh et al investigated biosorption of chromium (VI) ions on the different filamentous funguses including C. vulgaris, C. crispata, R. arrhizus, S. cerevisiae and Z. ramigera and maximum adsorption capacity was found to be 4.5mg/g [44]. Variations with respect to tolerance to Cr by fungi and bacteria were reported by earlier workers [4, 25, 27-34].

4. concluSIonS

The fungi and bacterial isolates showing maximum tolerance up to 100 ppm for one of the Pb, Cd and Cr metals are tested for potential microbes to remove these heavy metals

Table 1: Uptake of Pb by different fungi from liquid medium containing 50 ppm Pb.

Fungi uptake (mg/g)

FPb5 (Aspergillus sp.) 5.86

Aspergillus nidulans 25.67

F Pb 17 (Aspergillus sp.) 10.25

F Pb 19 (Aspergillus sp.) 17.38

Penicillium chrysogenum 11.55

Aspergillus flavus 12.45

Trichoderma viride 9.14

Table 2: Uptake of Pb by different bacterial isolates from liquid medium containing 50 ppm Pb.

Bacteria uptake (mg/g)BPb6 19.38

BPb8 18.20

BPb9 8.94

BPb12 45.08

BPb16 43.80

BPb17 5.27

BPb18 6.50

BPb21 5.56

BPb22 6.72

BPb23 1.19

BPb24 0.69



219

Table 3: Uptake of Cd by different fungi from liquid medium containing 50 ppm Cd.

Fungi uptake (mg/g)23Cd F (A.sp.) 4.20

24 Cd F (A.sp.) 4.16

Aspergillus flavus 1.38


Rhizopus arrhizus 13.15

Table 4: Uptake of Cd by different bacterial isolates from liquid medium containing 50 ppm Cd.

Bacteria uptake (mg/g)BCd1 0.38

BCd2 1.37

BCd5 2.12

BCd9 0.34

Table 5: Uptake of Cr by different fungi from liquid medium containing 50 ppm Cr.

Fungi uptake (mg/g)

Trichoderma viride 2.55

Aspergillus nidulans 0.04


Rhizopus arrhizus 0.23

Table 6: Uptake of Cr by different bacterial isolates from liquid medium containing 50 ppm Cr.

Bacteria uptake (mg/g)

BCr1 0.27

BCr14 3.29

BCr15 0.34

BCr17 0.11

Kumar, R.Singh, P.


220

from liquid medium and the most efficient microbes for removal of heavy metals from liquid media are identified. Further studies to realize their potential for removal of heavy metals from industrial effluents are in progress.

AcKnowleDgeMentS

One of the authors Prem Singh acknowledges the financial assistance in the form of minor research project from University Grants Commission, New Delhi.

ReFeRenceS

[1] A. Malik, “Metal bioremediation through growing cells,” Environmental International Journal 30, 261-278 (2004). http://dx.doi.org/10.1016/j.envint.2003.08.001

[2] T.G. Chuah, A. Jumasiah, I. Azni, S. Katayon and S.Y.T. Choong, “Rice husk as a potentially low-cost biosorbent for heavy metal and dye removal: an overview,” Desalination 175, 305-316 (2005). http://dx.doi.org/10.1016/j.desal.2004.10.014

[3] J.A. Brierley, C.L. Brierley, and G.M. Goyak, “AMT-BIOCLAIM: A new wastewater treatment and metal recovery technology. In: Fundamental and Applied Biohydrometallurgy, Eds. R.W. Lawrence, R.M.R. Branion and G. Ebner, Elsevier, Amsterdam 291-303 (1986).

[4] M. Nourbakhsh, Y. Sag, D. Ozer, Z. Aksu, T. Katsal and A. Calgar, “A comparative study of various biosorbents for removal of chromium (VI) ions from industrial wastewater,” Process Biochemistry 29, 1-5 (1994). http://dx.doi.org/10.1016/0032-9592(94)80052-9

[5] L.E. Macaskie, “The application of biotechnology to the treatment of wastes produced from the nuclear fuel cycle: biodegradation and bioaccumulation as a means of treating radionuclide containing streams,” Critical Reviews in Biotechnology 11, 41-112 (1991). http://dx.doi.org/10.3109/07388559109069183

[6] S.A. Churchill, J.V. Walters and P.F. Churchill, “Sorption of heavy metals by prepared bacterial cell surfaces,” Journal of Environmental Engineering 121, 706-711 (1995). http://dx.doi.org/10.1061/(ASCE)0733-9372(1995)121:10(706)

[7] G.M. Gadd, “Fungi and yeasts for metal accumulation,” In Microbial Mineral Recovery, Eds. H.L. Ehrlich and C.L. Brierle, McGraw-Hill, New York, 249-276 (1990).

[8] F. Veglio and F. Beolchini, “Removal of metals by biosorption: a review,” Journal of Hydrometallurgy 74, 301-316 (1997).

http://dx.doi.org/10.1016/S0304-386X(96)00059-X

[9] K.M. Elizabeth and T.V.R. Anuradha, “Biosorption of hexavalent chromium by non-pathogenic bacterial cell preparations,” Indian Journal of Microbiology 40, 263-265 (2000).

[10] S.R. Bai, and T.E. Abraham, “Studies on chromium (VI) Adsorption – desorption using immobilized fungal biomass,” Bioresource Technology 87, 17-26 (2003).

http://dx.doi.org/10.1016/S0960-8524(02)00222-5

[11] A.E. Greenberg, R.R. Trussell, and L.S. Clesceri, “Standard methods for the examination of water and wastewater, 16th edition,” American Public Health Association, Washington, DC, 146-150 (1985).

221

[12] S. Solarsk, T. May, F.A. Roddick and A.C. Lawrie, “Isolation and screening of natural organic matter-degrading fungi, Chemosphere 75, 751-8 (2009).

http://dx.doi.org/10.1016/j.chemosphere.2009.01.030

[13] V.S.K.V. Rama Rao, N. Akhtar and M.P. Maruthi, “Isolation of a cadmium tolerant Curvularia sp. for polluted effluent,” Current Science 73, 453 (1997).

[14] J.S. Chang, R. Law and C.C. Chang, “Biosorption of lead, copper and cadmium by biomass of Pseudomonas Aeruginosa PU 21,” Water Research 31, 1651–1658 (1997). http://dx.doi.org/10.1016/S0043-1354(97)00008-0

[15] A. Kapoor, T. Viraraghavan and D.R. Cullimore, “Removal of heavy metals using the fungus Aspergillus niger,” Bioresource Technology 70, 95–104 (1999).

http://dx.doi.org/10.1016/S0960-8524(98)00192-8

[16] P.R. Puranik and K.M. Paknikar, “Biosorption of lead, cadmium and zinc by Citrobacter strain MCM B-181: characterization studies,” Biotechnology Program 15, 228-37 (1999). http://dx.doi.org/10.1021/bp990002r

[17] A.D. Costa, A. Carlos and F. Pereira, “Bioaccumulation of copper, zinc, cadmium and lead by Bacillus sp., Bacillus cereus, Bacillus sphaericus and Bacillus subtilis,” Brazilian Journal of Microbiology 32, 1-5 (2001).

[18] R. Pardo, M. Herguedas, E. Barrado and M. Vega, “Biosorption of cadmium, copper, lead and zinc by inactive biomass of Pseudomonas putida,” Analytical and Bioanalytical Chemistry 376, 26-32 (2003).

[19] A. Selatnia, A. Boukazoula, B.N. Kechid, M.Z. Bakhti, A. Chergui and Y. Kerchich, “Biosorption of lead (II) from aqueous solution by a bacterial dead Streptomyces rimosus biomass,” Biochemical Engineering Journal 19, 127-135 (2004).

[20] S.B. Choi, and Y.S. Yun, Lead biosorption by waste biomass of Corynebacterium glutamicum generated from lysine fermentation process. Biotechnology Letters 26, 331-336 (2004).

[21] S. Tunali, T. Akar, A. Safa Ozcan, I. Kiran and A. Ozcan,“ Equilibrium and kinetics of biosorption of lead (II) from aqueous solutions by Cephalosporium aphidicola” Separation and Purification Technology 47, 105-112 (2006).

[22] M.I. Kefala, A.I. Zouboulis and K.A. Matis, Biosorption of cadmium ions by actinomycetes and separation by flotation. Environmental Pollution 104, 283-293 (1999).

[23] H.A. Ghoslan, S.A. Sabry, and R.A. Amer, “Bioaccumulation of nickel, cobalt and cadmium by free and immobilized cells of Pseudomonas sp,” Fresenius Environmental Bulletin 8, 428-435 (1999).

[24] R. Say, A. Denizli and M.Y. Arica, “Biosorption of cadmium (II), lead (II) and copper (II) with the filamentous fungus Phanerochaete chrysosporium,” Bioresource Technology 76, 67-70 (2001).

[25] M. Watanabe, K. Kawahara, K. Sasaki and N. Noparatnaraporn, “Biosorption of cadmium ions using a photosynthetic bacterium, Rhodobacter sphaeroides S and a marine photosynthetic bacterium, Rhodovulum sp. and their biosorption kinetics,” Journal of Bioscience and Bioengineering 95, 374-378 (2003).

[26] G. Ozdemir, N. Ceyhan, T. Ozturk, F. Akirmak and T. Cosar, “Biosorption of chromium (VI), cadmium (II) and copper (II) by Panteo sp. TEM18,” Journal of Chemical Engineering 102, 249-253 (2004).

222

[27] H.Y. Qi, Q. Hu, M.N. Dou and J.H. Zeng, “Biosorption of Cd2+ by a hyper resistant newly isolated Bacillus cereus strain,” In 11th International Symposium on Microbial Ecology Vienna, Austria, Abstract, p 79, (2006).

[28] Z. Aksu, T. Kutsal, S. Gun, N. Haciosmanoglu and M. Gholaminejad, “Investigation of biosorption of Cu (II), Ni (II) and Cr (VI) ions to activated sludge bacteria,” Environmental Technology 12, 915-921 (1991).

[29] C. Solisio, A. Lodi, A. Converti and M. Del Borghi, “The effect of acid pre-treatment on the biosorption of chromium (III) by a Sphaerotilus natans from industrial wastewaters,” Water Research 34, 3171-3178 (2000).

[30] T. Srinath, T. Verma, P.W. Ramteke and S.K. Garg, “Chromium (VI) biosorption and bioaccumulation by chromate resistant bacteria” Chemosphere 48, 427-435 (2002).

[31] A. Iyer, K. Mody and B. Jha, “Accumulation of hexavalent chromium by an exopolysaccharide producing marine Enterobacter cloaceae,” Marine Pollution Bulletin 49, 974-977 (2004). http://dx.doi.org/10.1016/j.marpolbul.2004.06.023

[32] T. Akar, and S. Tunali, “Biosorption characteristics of Aspergillus flavus biomass for removal of Pb (II) and Cu (II) ions from an aqueous solution,” Bioresource Technology Vol. 97, 1780-1787 (2006). http://dx.doi.org/10.1016/j.biortech.2005.09.009

[33] B. Preetha and T. Viruthagiri, “Batch and continuous biosorption of chromium (VI) by Rhizopus arrhizus,” Separation Purification Technology 57, 126-133 (2007).

http://dx.doi.org/10.1016/j.seppur.2007.03.015

[34] J. Srivastava, H. Chandra, K. Tripathi, R. Naraian and R.K. Sahu, “Removal of chromium (VI) through biosorption by the Pseudomonas sp. isolated from tannery effluent” Journal of Basic Microbiology 48, 135-139 (2008). http://dx.doi.org/10.1002/jobm.200700291

[35] A.Y. Dursun, G. Uslu, Y. Cuci and Z. Aksu, “Bioaccumulation of copper (II), lead (II) and chromium (VI) by growing Aspergillus niger” Process Biochemistry 38 (12), 1647-1651 (2003). http://dx.doi.org/10.1016/S0032-9592(02)00075-4

[36] G. Resmi, S.G. Thampi and S. Chandrakaran, “Brevundimonas vesicularis: A Novel Bio-sorbent for Removal of Lead from Wastewater” International Journal of Environmental Research 4 (2), 281-288 (2010).

[37] R. Faryel, A. Sultan, F. Tahir, S. Ahmed and A. Hameed, “Biosorption of lead by indigenous fungal strains” Pakistan Journal of Botany 39(2), 615-622 (2007).

[38] W. Jianlong, Z. Xinmin, D. Decaib and Z. Dingc, “Bioadsorption of lead (II) from aqueous solution by fungal biomass of Aspergillus niger” Journal of Biotechnology 87(3), 273-277 (2001). http://dx.doi.org/10.1016/S0168-1656(00)00379-5

[39] P. Baldrian, J. Gabriel and F. Nerud, “Effect of cadmium on the ligninolytic activity of Stereum hirsutum and Phanerochaete chrysosporium” Folia Microbiologica, 41, 363–367 (1996). http://dx.doi.org/10.1007/BF02814716

[40] A. Hassen, N. Saidi, M. Cherif and A. Boudabous, “Effects of heavy metals on Pseudomonas aeruginosa and Bacillus thurengiensis” Bioresource Technology 65, 73-82 (1998).

http://dx.doi.org/10.1016/S0960-8524(98)00011-X

[41] E. Parameswari, A. Lakshmanan and T. Thilagavathi, “Chromate Resistance and Reduction by Bacterial Isolates” Australian Journal of Basic and Applied Sciences 3 (2), 1363-1368 (2009).

223

[42] M. Vasanthy, “An investigation on removal of chromium (VI) using bacterial strains” Asian Journal of Microbiology, Biotechnology and Environmental Sciences 6 (4), 583-586 (2004).

[43] A. Zahoor and A. Rehman, “Isolation of Cr (VI) reducing bacteria from industrial effluents and their potential use in bioremediation of chromium containing wastewater” Journal of Environmental Sciences 21 (6) 814–820 (2009).

http://dx.doi.org/10.1016/S1001-0742(08)62346-3

[44] M. Nourbakhsh, Y. Sag, D. Ozer, Z. Aksu, T. Kutsal and A. Caglar, “A comparative study of various biosorbents for removal of chromium(VI) ions from industrial waste waters’ Process Biochemistry 29, 1-5 (1994). http://dx.doi.org/10.1016/0032-9592(94)80052-9

[45] U. Yestis, G. Ozcengiz, F.B. Dilek, N. Ergen, A. Erbay and A. Dolek, “Heavy metal biosorption by white-rot fungi,” Water Science and Technology, 38(4-5), 323-330 (1998). http://dx.doi.org/10.1016/S0273-1223(98)00515-0

[46] H. Niu, X. S. Xu, and J.H. Wang, “Removal of lead from aqueous solutions by Penicillin biomass,” Biotechnology and Bioengineering, 42, 785-787 (1993).

http://dx.doi.org/10.1002/bit.260420615

[47] R. Say, A. Denizli and A. M. Yakup, “Biosorption of cadmium (II), lead (II) and copper (II) with the filamentous fungus Phanerochaete chrysosporium,” Bioresource Technology 76, 67-70 (2001). http://dx.doi.org/10.1016/S0960-8524(00)00071-7

[48] T. Akar and S. Tunali, “Biosorption performance of Botrytis cinerea fungal by-products for removal of Cd (II) and Cu (II) ions from aqueous solutions,’ Minerals Engineering 18, 1099-1109 (2005). http://dx.doi.org/10.1016/j.mineng.2005.03.002

potential of some fungal and bacterial species in bioremediation of heavy metals

Documents